This invention relates to a rail engagement apparatus for a road vehicle. More specifically, this invention relates to a rail engagement apparatus mountable upon a road vehicle to allow use of a vehicle suspension when the road vehicle is driven along a railway.
Railroad service crews often have to go to various places along a railroad track in order to make repairs and inspections. Depending upon the type of service which is to be performed and other factors, the service crew may ride to the work site using a rail vehicle or using a road vehicle, such as a truck or car. Since the best way to a work site may include travel along a road and travel along a railway, service crews and other rail workers often have used road vehicles having a rail engagement apparatus mounted on them. Such cars or trucks may travel along a highway or other road with road wheels engaging the road. Upon getting to an appropriate place along the railway, the rail engagement apparatus is operated such that railway wheels are lowered from the vehicle until the vehicle is bound to the railway. Usually such vehicles include an apparatus at the front of the vehicle which lifts the front road wheels off the ground when two front railway wheels engage rails and an apparatus at the back of the vehicle, which apparatus secures the back of the vehicle to the rails by two back railway wheels. The two back railway wheels usually allow the regular road wheels to contact the rails or other surface such that the road wheels may provide traction to move the vehicle even when the two front railway wheels and two back railway wheels have secured the vehicle to the rail. When the vehicle wishes to leave the railway, the two front railway wheels and the two rear railway wheels are retracted or lifted up such that the vehicle may again run along the road.
Various structures have been used to allow railway wheels to be attached to road vehicles. Although such structures have been generally useful at moving the railway wheels between an upper position in which the vehicle may travel along a highway or other road and a lower position in which the vehicle would travel along a railway, such structures have often been subject to one or more of several disadvantages. Such structures are often quite heavy. One of the reasons that these structures are often quite heavy is that they often include a shock absorption system to absorb shocks when the railway wheels are engaged with rails.
Prior U.S. Pat. No. 4,488,494 issued Dec. 18, 1984 to Powell discloses a rail engagement apparatus for a road vehicle wherein the rail engagement apparatus uses the shock absorption arrangement already in the vehicle suspension for absorbing shocks when the railway wheels are engaged. Thus, one need not use a separate system in the rail engagement apparatus for absorbing vibration. However, the rail engagement apparatus of Powell is attached to the vehicle suspension and will increase the undesirable unsprung weight of the vehicle. (The unsprung weight is the weight of those parts of the vehicle which receive vibrations from the vehicle contact with the rolling service without the vibrations being dampened by the shock absorption arrangement vehicle suspension.) This unsprung weight increase changes the handling characteristics of the vehicle even for road operations.
Various other structures which have been used to allow road vehicles to travel along railways have often had reliability or maintenance problems, high cost due to complex construction, and instability in operation.